Centrifugal pump with dual impeller



Feb 11, 1941. Q Q ACOBSEN 2,231,720

CENTRIFUGAL PUMP WITH DUAL IMPELLER Filed Sept. 16, 1939 2 Sheets-Sheet 1 invemk r OYsTEm Jncossm M; town @ys WSMLMTSW- Feb. 11, 1941. Q ACOBSEN 2,2317% CENTRIFUGAL PUMP WITH DUAL IMPELLER Filed Sept. 16, 1939 2 Sheets-Sheet 2 11 2 a as 1.0 9 31 go an Knvmmv QYBTHN JRCOEN by flktornzys Patented Feb. 11, 1941 Oystein Jacobsen, Montgomery County,

Duriron Company, Inc.,

signor to Th Ohio, as Dayton,

Ohio, a corporation of New York Application September 16, 1939, Serial No. 295,321

4 Claims.

The present invention relates to centrifugal pumps, and more especially to pumps designed to operate at considerable velocities and adapted to handle acids or water containing acids. The present invention represents an improvement over the apparatus shown and described in my prior application, Ser. No. 229,470, filed September 12, 1938, which is assigned to the same assignee as the presentlnvention.

In the application referred to, there is disclosed a centrifugal pump having means for preventing the flow of corrosive fluid, such as acid, along the drive shaft and through the packing thereof. This prevention of'flow was brought about by introducing into the pump a jet-action which served to withdraw or evacuate the fluid which normally collects at the pockets be-v tween the impeller and the thrust plate. This jet-action was produced by closing the inner ends of several pairs of the arcuate vanes, and providing at the closed ends thereof an opening through which fluid was drawn at a high velocity to cause a sucking efiect on the leakage fluid which gained access to the pump through a large opening in the impeller plate. Thus, the opening at the closed end of the arcuate compartments not only received a considerable amount of fluid which normally passes through the compartment or passageway, but also additional fluid which represents the leakage fluid passing through the opening in the impeller plate.

While a pump such as described operates quite satisfactorily from the standpoint of relieving the pockets between the impeller plate and thrust plate of the leakage fluid which might eventual- 1y find its way to the stufling box, I have found in accordance with the present invention that the jet-action of the closedvane compartment may be considerably enhanced, necessitating only a relativelysmall change in the structure so that greater quantities of leakage fluid may be drawn through the compartment and thus the opportunity for this fluid to leave the pump throughthe packing box is still further minimized.

Due to this enhancement in the suction effect exerted by the closed vane compartment in accordance with the present invention, the number of pairs of vanes which are closed to provide the suction of leakage-fluid may be materially reduced without reducing the suction effect; It will be understood that when a pair of vanes are closed by an apertured member at their inner ends to provide a jet-action on the leakage fluid,- this compartment will not be completely filled with fluid since the amount of fluid would be determined by the size of the relatively small opening in the closure member. Thus the compartment is not operating at the same efliciency as the passageways between those vanes which have not been closed oii at their inner ends. Consequently, the smaller the number of compartments which are necessary to introduce a sufllcient jet-action on the leakage fluid, the greater will be the number of vane passageways which are completely filled with fluid and therefore, the greater will be the output of the pump.

Accordingly, the primary object of the present invention is to increase the suction effect on the leakage fluid exercisedby the closed vane compartment elements of a pump such as described in my earlier application to the end that the number of closed vane; compartments necessary for the 'suctiorieffect is minimized and as many as possible of the vanes are left open at their inner ends in order to obtain maximum output from the pump without detracting from the suction effect exercised on the leakage fluid;

It has been found that when the pump is rotated at high speeds, zones of contraction appear at the'irmer ends of the vanes and these zones represent pockets of vacuum. These zones of contraction are formed particularly when the direction of the fast-moving fluid is abruptly changed or when the fluid passes from a section of large cross-sectional area to a section of smaller cross-sectional area.

The object set forth above is attained, in brief, by providing at the inner end of the closed vane compartment not only an opening which provides the jet-action described in my prior application,

.a pair of openings, one of which produces the jet-action in accordance with my'prior invention, and the other provides an enhancement of this jet-action. The enhanced effect obtained by this second opening is so pronounced that I have obtained the same suction efiect by closing off the ends of only two pairs of vane compartments than had previously been obtained byclosing off the ends of four or more compartments. In other words, the effect of the second opening increases the jet-action on the leakage fluid to such an extent that no more than two pairs of closed end compartments are necessary to rid the impeller of all leakage fluid and thus the remaining vanes are left open at their inner ends to perform, the regular function of pumping the useful fluid.

The invention will be better understood when reference is made to the following description and the accompanying drawings in which- Figure 1 represents a vertical cross section taken through the middle of the improved pump.

Figure 2 is an elevational view, partly broken away, the section being taken along the line 22 in Figure 1 and looking in the direction of the arrows.

Figure3 is a partly elevational perspective view and partly a sectional view, taken along the line 33 in Figure 1 and looking in the direction of the arrows.

Figures 4 and 5 are enlarged cross sectional views of the inner portion of the vane structure and immediately adjacent parts useful in explaining the manner lnwhich certain improvements provided by this invention serve to increase the efficiency of the pump. Figure 4 shows the effect obtained without the improvement, while Figure 5 illustrates the enhancedresuit obtained by the improvement described hereinafter.

Referring to the drawings in detail, numeral l designates a spaced pair of heavy discs or plates of an acid-resisting metal, such as silicon iron, between which is secured in any suitable manner,

as for example by casting, a number of arcuate vanes 2, as seen more clearly in Figure 1. The plates I are carried on a central hub 3, which has an opening to receive the tapered-down portion of a drive shaft 4. The shoulder of the shaft, as indicated at 5, bears against the flat end surface of the hub 3. The drive shaft 4 may be secured to the hub 3 in any suitable manner, for example, by threading, with special attention given to the direction of rotation of the impeller which constitutes the plates i and vanes 2 and which will be hereinafter designated generally by the reference character 6.

The impeller 6 is adapted to rotate at a high rate of speed within a heavy casting I, which provides thrust bearing surfaces 8 spaced apart and of relatively small width, to reduce frictional losses. These bearing surfaces introduce pockets, indicated at 9, which inevitably collect fluid leaking from the periphery of the impeller. The casting 1 is provided with an outwardly extending flange l0, cored out so as to receive a packing box ll, exemplified by.v a plurality of discs of packing material which surrounds the drive shaft. The casting I has an inwardly extending shoulder, as indicated at 12, which serves as a stop for the packing II. A shoulder I3 is provided on the casting 1 to receive a pump support member M, by which the pump is secured to a suitable foundation. The casting 1 takes on a volute shape, as indicated in Figure 1, the size of the volute being considerably larger than the outside diameter of the impeller 6. The volute chamber formed within the casting 1 is drawn down to a discharge port I5, of approximately circular configuration; which terminates in an enlarged outlet end l6 engaged by a clamping ring I! for securing thereto a discharge conduit.

The right-hand end plate of the casting I, as shown in Figure 2 and designated by the reference character [8, is provided with a large opening l9 and a narrow bearing surface 20. There is a hollow casting 2|, which bears against the surface 20 and is separated therefrom by a gas-. ket 22 for preventing the leakage of fluid. The casting 2| may be secured to the casting 1 in any suitable manner, and as illustrated there is provided a circular ring 23 which carries bolts 24, the latter extending through the ring 23 and being secured to the pump support 14. The casting 2| is provided with an intake extension 25 and an intake chamber 26, containing vanes 21 for preventing the swirling of the fluid entering the pump. The outer end 28 of the intake extension 25 is enlarged, and engaged by a clamping ring 29 for the purpose of securing thereto an intake conduit. The lower end of the casting 1 is provided with a drainage extension 30, having a drainage port 3i closed by a plate 32 and held in position by the U-bolt 33.

The vanes 2, as seen more clearly inFigure 1, are of a general spira1 configuration, the direction of the spiral being dependent on the directionof rotation of the impeller. The passageways formed between the vanes may be broadly termed Venturi-shaped in that ther is provided a throat portion 34 and also an outlet portion 35. Thus, these vanes divide the interior of the impeller into alternately arranged vane chambers, which at their inner ends open into the intake passageway 36 communicating with the pump intake chamber 26. The outer or peripheral portions 35 of the vanes are in communication with the volute chamber formed within the casting I so that as the impeller is rotated counterclockwise, as seen in Figure 1, fluid is drawn through the intake port 26 and is discharged through the outlet port l5 at a velocity depending on the speed of rotation of the impeller.

It was pointed out hereinbefore that there are pockets 9 formed between the left-hand side plate i (as seen in Figure 2) and the casting 1, these pockets being necessary in order to reduce the width of the bearing surfaces 8. As the fluid is being forced by the rotating impeller through the discharge port IS, a small portion thereof tends to run downwardly between the impeller and the casting 7 at the bearing surfaces 8. It will be understood that there must be a small space left between the side walls of the impeller and the casting I, at the bearing surfaces, in order to minimize friction. Thus, this fluid reaches first the outer pocket 9 and then collects in the inner pocket, where it is in a good position to travel along the drive shaft and from there into the packing box I l. Eventually, this leakage fluid might find its way to a position remote from the pump, and in case it is of a corrosive nature will deleteriously affect other apparatus associated with the pump, for example, the electric motor drive. In order continuously to drain at least the lower or inner pocket 9 of this leakage fluid, there is provided one or more openings 31 in the nearest side wall I of the impeller.

These openings communicate with one or more of the passageways formed between the vanes 2, and preferably at a position at the inner ends of these vanes. In order to provide a suction effect on this leakage fluid, at least one pair of vanes 2, as shown in Figure 1, have their inner ends closed by a closure member 38 to form compartments 39, which are substantially closed at one end but are left freelyopen at the other end. A jet-action is produced at the closure member 38 by means of an opening 40, which is so positioned with respect to the closure member that the fluid introduced at the impeller flows freely through the opening into the compartment 39. In passing through this opening, and eventually through the compartment into the volute chamber, this fluid produces a strong sucking or evacuation effect which causes the leakage fluid from the inner pocket 9 to flow through the opening 31 and out through the compartment 39, to the discharge port l5. Thus, as the impeller rotates, a steady drainage takes place at the inner pocket 9, due to the jet-action referred to, and there is no fluid to travel along the drive shaft and through the packing box to the exterior of the pump. The packing material, therefore, remains in a lubricated condition, and effectively serves to prevent any but very slight leakage which cannot otherwise be avoided.

The subject-matter up to this point has been disclosed and claimed in my copending application Ser. No. 229,470, and the structure has been illustrated in Figure 4. As stated hereinbefore, a

pump structure of this character has operated satisfactorily, but it has been found that in order to obtain a sufilcient suction effect on the leakage fluid which collects between the impeller and the thrust plate, it is necessary to provide a number of these closed end compartments in order to obtain a sufficient jet-action. However, as will be explained presently, I am enabled to obtain enhanced suction or jet-action effect by modifying the construction of the compartment to such an extent that the number of these compartments may be reduced.

The improvement is shown in Figure 5. In this figure it will be noted that in additionto the opening 40, there is provided at the end of the compartment an additional opening 42. This additional opening is positioned in the region of the zone of contraction, which zones of contraction appear at the inner ends of the arcuate vanes. These zones of contraction are indicated in Figures 4 and by the-reference character 4|. They represent the position at which air collects which is driven out of the fluid and produces a pocket.

The pressure in this pocket is equal to the fluid pressure surrounding the pocket.

While the position of the opening 42 may be anywhere within the region of the opening 40 so as to form a passageway between the closed compartment and the next adjacent passageway, I have found that the best results are obtainable when this opening is positioned at the zone of contraction. As stated hereinbefore, the opening 42 serves considerably to enhance the suction or evacuation effect exercised on the leakage fluid which passes through the opening 31 into the closed compartment. While I do not wish to be limited to any theory as to the cause of this enhancement, I believe that the opening 42 serves to transfer some of the suction effect present between the open vane compartment into the closed vane compartment. It is, of course, well known that when a centrifugal pump provided with arcuate vanes of a spiral configuration is rotated in a direction away from the angle of the spiral, which in the case of the arrangement shown in Figure 1 would be counterclockwise, there is a strong suction effect exerted by the moving vanes, and this suction effect may be exerted on any fluid within the pump, whether it is air or liquid. Thus, as the vanes move counterclockwise a vacuum tends to be created in the passageways between the vanes, and this vacuum can be transferred through the opening 42 to assist the jetaction effect exerted by the opening 40. This enhanced suction or evacuation effect is so strong that it has been found unnecessary to-provide more than two closed compartments through which the leakage fluid is sucked from the pockets 9, through the openings 31, and is expelled at the periphery of the compartment 39. Since no more than two of these closed end compartments are necessary to relieve the pockets 9. of the leakage fluid, .the passageways between the remaining vanes may be left open at their inner ends andv consequently filled with the useful fluid.

It will be understood that the closed end compartment 39 is not fllled with useful fluid because of the'restriction at the opening 49, and the additional leakage fluid passing up through the opening 31 is not sumcientto entirely fill the compartment. The fact that the compart ment 39 is not completely fllled with fluid has been indicated in Figures 4 and 5 by the absence of the small curved lines at the top of the compartment. Consequently, by minimizing or reducing the number of closed end compartments which are necessary to eliminate all leakage fluid from the pockets 9, and by increasing the efficiency of these closed end compartments by the additional opening 42, the number of remaining compartments which are completely filled with useful fluid is correspondingly increased. The improved pump, therefore, has a greater output for a given size of impeller.

From the practical standpoint, I have found that the provision of the opening 42, in producing an enhancement of the jet-action introduced by the opening 40, is so pronounced that an increase in the suction opening 31 of the pump may be as high as ten to fifteen per cent. The

optimum size of the openings 40 and 42, by which this increased suction effect is produced, is best determined by experiment, and as stated hereinbefore, the position of the opening 42 should preferably be in the region of the zone of contraction 4|. The opening 42 represents a small change in structure, and obviously this opening may be provided in the closeure member at the time the opening is produced.

It will be understood that I desire to comprehend within my invention such modifications as come within the scope of the claims and the invention.

Having thus fully described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. A fluid pump of the centrifugal type comprising a casing containing a plurality of vanes secured tothe shroud of an impeller, an'inlet passageway leading from the exterior of the casing to the center of the impeller and communicating with the passageways between the vanes, an outlet passageway leading from the periphery of the impeller, said impeller being rotatably mounted adjacent to a thrust plate, and means for draining the fluid which collects between the impeller and the thrust plate and for causing the fluid to flow into the passageways between the vanes, said means including a closure member across the inner ends of at least: one pair of vanes to form a compartment which opens into the outlet passageway, said inlet passageway having a larger area than the vane passageways whereby a zone of contraction is normally produced at the junction between the inlet and vane passageways, said closure member having an aperture which opens into the adjacent vane passageway at the position of said zone of contraction, said means also including a passageway through the impeller shroud communicating with the space to be drained and located within the compartment closely adjacent the aperture in the closure member.

2. A fluid pump of the centrifugal type comprising, a casing containing a plurality of vanes secured to the shroud of an impeller, an inlet passageway leading from the exterior of the casing to the center of the impeller and communicating with the passageways between the vanes, an outlet passageway leading from the periphery of the impeller, said impeller being rotatably mounted adjacent to a thrust plate, means for draining the fluid which collects between the impeller and the thrust plate and causing the fluidto flow into the passageways between the vanes, said means including a closure member across the inner ends of at least one pair of vanes to form a compartment which opens into the outlet passageway, said inlet passageway having a larger area than the vane passageways whereby a zone of contraction is normally produced at the junc-' tion between the inlet and vane passageways, said means includinga pair of apertures in said closure member, one of said apertures opening into said inlet passageway and the other of said apertures opening into the adjacent vane passageway at the position of said zone of contraction, both of said apertures being in communication with a passageway through the impeller shroud which communicates with the space to be drained and located within the compartment closely adjacent the apertures in the closure member.

3. A fluid pump of the centrifugal type comprising a casing containing a plurality of vanes secured to an impeller, an inlet passageway leading from the exterior of the casing to the center of the impeller communicating with the passageways between the vanes, an outlet passageway leading from the periphery of the impeller, means including a shaft and a stufling box for rotatably mounting said impeller, means for preventing fluid from leaking along the shaft into the stufling box, said means including an apertured closure member across the inner ends of at least one pair of vanes to form a compartment which opens intothe outlet passageway, said means also including an opening in the impeller in the region of the stumng box, said opening communicating with the aperture in said closure member whereby a suction eiIect is introduced by said aperture to cause the leakage fluid to flow through said opening in the impeller and to be expelled at the periphery of said compartment, said inlet passageway having a larger area than the vane passageways whereby a zone of contraction is normally produced at the Junction between the inlet and vane passageways, and

means for increasing the suction eilect on the leakage fluid in said'compartment, said means including a s'econdaperture in said closure member positioned in the region of said zone of contraction. I

4. A fluid pump of the centrifugal type comprising a casing containing an impeller, vanes secured thereto, an opening in the side oi the impeller to withdraw leakage fluid which collects between the impeller and the casing, an inlet passageway leading from the exterior of the casing to the center of the impeller and communicating with the passageways between the vanes, an outlet passageway leading from the periphery of the impeller, said inlet passageway having an angular direction with respect to the direction of the vane passageways whereby a zone-of contraction is produced in the region of the junction between the inlet and vane passageways, and an opening through the wall of at least one of the vanes and positioned in the region of the 'zone of contraction and communicating with the opening in the side of the impeller.

' OYSTEIN JACOBSEN 

